I'm planning on getting my basement finished and decided to put a dedicated home theater room in the plans.
The dimensions are 15' 6" W x 21' 3" L x 8' 5" H
Listening preference will be 80% movies, 20 % music
I want to get the room prewired for a 7.2 speaker setup but was wondering what you would recommend for speakers in each.
The speakers would be slowly bought first and then the electronics (TV, receiver, DAC, maybe preamp) the following year.

Debating on the RTi's or the LSi M's

If I had to get the electronics right now, it would be something like this:

Don't even consider rear surrounds. Maybe consider wides instead. Why you ask? Good question, not only do you widen your sound stage, you increase your sound in your front stage. My room was close to yours at 15.5 wide and accommodated four RTiA9's and a pair of Epic Empires. I have both the XPA2 and 3, my FXiA6's were fed by my AVR, check it.

Spinning the rear tire at 150mph while at 3/4 lean angle will put wrinkles in your seat